package com.hmdp.utils;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.entity.Shop;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

@Slf4j
@Component
public class CacheClient {
    private final StringRedisTemplate stringRedisTemplate;

    public CacheClient(StringRedisTemplate stringRedisTemplate) {
        this.stringRedisTemplate = stringRedisTemplate;
    }

    //设置TTL过期时间
    public void set(String key, Object value, Long time, TimeUnit unit){
         stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value), time, unit);
    }

    //设置逻辑过期时间
    public void setWithLogicalExpire(String key, Object value, Long time, TimeUnit unit){
        RedisData redisData = new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)));
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(redisData));
    }

    //缓存空值解决缓存穿透
    public <R, ID> R queryWithPassThrough(
            String keyPrefix, ID id, Class<R> type, Function<ID, R> dbFallBack,
            Long time, TimeUnit unit) {
        //1.从redis中查询商铺缓存
        String key = keyPrefix + id;
        String json = stringRedisTemplate.opsForValue().get(key);

        //2.判断是否存在
        if(StrUtil.isNotBlank(json)){
            //3.存在, 直接返回商铺信息
           return JSONUtil.toBean(json, type);
        }
        //判断命中的是否是空字符串
        if(json != null){
            return null;
        }

        //4.不存在, 查询数据库
        R ret = dbFallBack.apply(id);

        //5.不存在,返回错误
        if(ret == null){
            //将空值写入redis
            stringRedisTemplate.opsForValue().set(key, "", RedisConstants.CACHE_NULL_TTL, TimeUnit.MINUTES);
            return null;
        }

        //6.存在,写入redis,返回数据
        this.set(key, ret, time, unit);
        return ret;
    }

    private boolean tryLock(String key) {
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }
    private void unlock(String key){
        stringRedisTemplate.delete(key);
    }

    private static final ExecutorService CACHE_REBUILD_EXECUTOR  = Executors.newFixedThreadPool(10);
    public <R, ID> R queryWithLogicalExpire(String cachePrefix, ID id, Class<R> type, String lockPrefix,
                                            Function<ID, R> dbFallBack,Long time, TimeUnit unit) {
        //1.从redis中查询商铺缓存
        String key = cachePrefix + id;
        String json = stringRedisTemplate.opsForValue().get(key);

        //2.未命中返回空
        if(StrUtil.isBlank(json)){
            return null;
        }

        //3.命中, 先把json字符串反序列化为对象
        RedisData redisData = JSONUtil.toBean(json, RedisData.class);
        JSONObject data = (JSONObject) redisData.getData();
        R ret = JSONUtil.toBean(data, type);
        LocalDateTime expireTime = redisData.getExpireTime();
        //4.判断是否过期
        if(expireTime.isAfter(LocalDateTime.now())){
            //5.未过期, 返回店铺信息
            return ret;
        }

        //6.已过期,需要进行缓存重建
        //6.1 获取互斥锁
        String lockKey = lockPrefix + id;
        boolean isLock = tryLock(lockKey);
        if(isLock){
            //6.2 获取锁成功 开启独立线程,进行缓存重建
            CACHE_REBUILD_EXECUTOR.submit(()->{
                try {
                    //缓存重建
                    //1.查询数据库
                    R result = dbFallBack.apply(id);
                    //2.添加到缓存
                    this.setWithLogicalExpire(key, result, time, unit);

                } catch (Exception e){
                    throw new RuntimeException(e);
                }finally {
                    //释放锁
                    unlock(lockKey);
                }

            });
        }

        //6.3 返回过期的商品信息
        return ret;
    }
}
